Avago Technologies LSI53C1000R - Manual (Page 22)

1-4 Introduction
Version 2.2 Copyright © 2000–2003 by LSI Logic Corporation. All rights reserved.
1.2 Benefits of Ultra160 SCSI
Ultra160 SCSI delivers data up to two times faster than Ultra2 SCSI.
Ultra160 SCSI is a subset of Ultra3 SCSI, which is an extension of the
SPI-3 draft standard. When enabled, Ultra160 SCSI performs
80 megatransfers/s, resulting in approximately double the synchronous
data transfer rates of Ultra2 SCSI. The LSI53C1000R performs 16-bit,
Ultra160 SCSI synchronous data transfers as fast as 160 Mbytes/s. This
advantage is most noticeable in heavily loaded systems, or large block
size applications such as video on-demand and image processing.
The Ultra160 data transfer speed is accomplished using DT clocking.
DT clocking refers to transferring data on both polarity edges of the
request or acknowledge signals. Data is clocked on both rising and falling
edges of the request and acknowledge signals. Double-edge clocking
doubles data transfer speeds without increasing the clock rate.
Ultra160 SCSI also includes CRC, which offers higher levels of data
reliability by ensuring complete integrity of transferred data. CRC is a
32-bit scheme, referred to as CRC-32. CRC is guaranteed to detect all
single bit errors, any two bits in error, or any combination of errors within
a single 32-bit range.
AIP is also supported by the LSI53C1000R, protecting all nondata
phases, including command, status, and messages. CRC, along with AIP,
provides end-to-end protection of the SCSI I/O.
SURElink domain validation provides 3 levels of integrity checking:
Basic (level 1), Enhanced (level 2), and Margined (level 3). Further
information on SURElink technology is available in
Section 1.3, “Benefits
of SURElink (Ultra160 SCSI Domain Validation) Technology.”
An advantage of Ultra160 SCSI is that it significantly improves SCSI
bandwidth while preserving existing hardware and software investments.
The primary software changes required are to enable the chip to perform
synchronous negotiations for Ultra160 SCSI rates and to enable the clock
quadrupler. Ultra160 SCSI uses the same connectors as Ultra SCSI and
Ultra2 SCSI.
Chapter 2, "Functional Description" contains more
information on migrating an Ultra SCSI or Ultra2 SCSI design to an
Ultra160 SCSI design.